This invention pertains to a mechanism used in pneumatic transfer of lading for closing and opening the discharge opening at the bottom of a hopper particularly for use with plastic pellets or granular material.
This type of material is generally difficult to discharge from containers with present type of valving comprising complex gates and operating mechanisms for closing the hopper and in discharging from the hopper. Particles of the material will bridge a portion of the discharge opening of the chute. In vacuum discharge arrangements upon malfunctioning when bridging occurs, the air is aspirated through a bypass passageway formed in the hopper alongside a static remaining pile of bridged material and flows into the discharge chute, thus preventing discharge of the material. This may cause the train personnel to climb on top of the car and poke the pile loose into the gate and thus close the bypass passageway so that the vacuum system can draw the material falling from the hopper.
In normal operation air is passed through the discharge tube at the bottom of the hopper outlet opening and the material cascading from the hopper is entrained in the air steam and drawn out from a discharge end of the tube while the air is being drawn into the other end of the tube. If the material builds up below the hoppers discharge opening, probes are used to disperse the compacted material into the air steam.